Paints For Exterior

Masonry Walls

i

I

BUILDING MATERIALS AND STRUCTURES REPORT BMSllO

UNITED STATES DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
BUILDING MATERIALS AND STRUCTURES REPORTS

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The following publications in this series are available by purchase from the

Superintendent of Documents at the prices indicated:

BMSl Research on Building Materials and Structures for Use in Low-Cost Housing 10^ BMS2 Methods of Determining the Structural Properties of Low-Cost House Constructions 10^ BMS3 Suitability of Fiber Insulating Lath as a Plaster Base 16^

BMS4 Accelerated Aging of Fiber Building Boards 10^

BMS5 Structural Properties of Six Masonry Wall Constructions 15^

BMS6 Survey of Roofing Materials in the Southeastern States 15^

BMS7 Water Permeability of Masonry Walls* * BMS8 Methods of Investigation of Surface Treatment for Corrosion Protection of Steel.. 10^

BMS9 Structural Properties of the Insulated Steel Construction Co.'s "Frameless-Steel"

Constructions for Walls, Partitions, Floors, and Roofs 10<f BMSIO Structural Properties of One of the "Keystone Beam Steel Floor" Constructions

Sponsored by the H. H. Robertson Co 10^

BMSll Structural Properties of the Curren Fabrihome Corporation's "Fabrihome" Constructions for Walls and Partitions 10^ BMS12 Structural Properties of "Steelox" Constructions for Walls, Partitions, Floors, and

Roofs Sponsored by Steel Buildings, Inc - 15c BMS13 Properties of Some Fiber Building Boards of Current Manufacture 10^

BMS14 Indentation and Recovery of Low-Cost Floor Coverings 10^

BMS15 Structural Properties of "Wheeling Long-Span Steel Floor" Construction Sponsored by the Wheeling Corrugating Co • 10^ BMS16 Structural Properties of a "Tilecrete" Floor Construction Sponsored by Tilecrete

Floors, Inc • 10^

BMS17 Sound Insulation of Wall and Floor Constructions 204

Supplement to BMS17, Sound Insulation of Wall and Floor Constructions 5^ BMS18 Structural Properties of "Pre-fab" Constructions for Walls, Partitions, and Floors,

Sponsored by the Harnischfeger Corporation 10^

BMS19 Preparation and Revision of Building Codes • • - BMS20 Structural Properties of "Twachtman" Constructions for Walls-and Floors Sponsored by Connecticut Pre-Cast Buildiners Corporation 10^

BMS21 Structural Properties of a Concrete-Block Cavity-Wall Construction Sponsored by

the National Concrete Masonry Association • • 10^

BMS22 Structural Properties of "Dun-Ti-Stone" Wall Construction Sponsored by the W.

E. Dunn Manufacturinsr Co 10^ BMS23 Structural Properties of a Brick Cavity-Wall Construction Sponsored by the Brick

Manufacturers Association of New York, Inc •4;"V","*m-r' BMS24 Structural Properties of a Reinforced-Brick Wall Construction and a Bnck-Tile

Cavity-Wall Construction Sponsored by the Structural Clay Products Institute 15^ BMS25 Structural Properties of Conventional Wood-Frame Constructions for Walls, Partitions. Floors, and Roofs ^^'^ SMS26 Structural Properties of "Nelson Pre-Cast Concrete Foundation" Wall Construetion Sponsored by the Nelson Cement Stone Co., Inc 10^ BMS27 Structural Properties of "Bender Steel Home" Wall Construction Sponsored by

the Bender Body Co

BMS28 Backflow Prevention in Over-Rim Water Supplies

BMS29 Survey of Roofing Materials in the Northwestern States • 15^ BMS30 Structural Properties of a Wood-Frame Wall Construction Sponsored by the

Douglas Fir Plywood Association • ••• '"^ BMS31 Structural Properties of "Insulite" Wall and "Insulite" Partition Constructions

Sponsored by The Insulite Co • *0trt of print. [List continued on cover page Hi]
Paints for Exterior Masonry Walls

by *

CLARA SENTEL

ISSUED NOVEMBER 15, 1947

Building Materials and Structures Report BMSllO

UNITED STATES DEPARTMENT OF COMMERCE • W. Averell Harriman, Secretary NATIONAL BUREAU OF STANDARDS • E. U. Condon, Director

I

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1947 FOR SALE BY THE SUPERINTENDENT OF DOCUMENTS. U. S. GOVERNMENT PRINTING OFFICE, WASHINGTON 25, D. C. PRICE 15 CENTS
Foreword

Data on the relative durability and performance of four general

classes of masonry paints are given in this report. Out-of-door

weathering tests were conducted to determine the serviceability of

paints applied to wall specimens constructed of new and used

common brick; cast concrete; stone-, cinder-, and lightweight-aggregate-concrete block; and wood frame with cement-asbestos

shingles.

Formulas for the paints and erection of the wall sections are

described, as well as methods for applying paint to the specimens.

Ratings based on the weathering characteristics and performance

of each type of paint and evaluation of painting methods for coat- ing diflferent surfaces are given.

Painted specimens which are discussed in detail in the body of

this report were exposed to atmospheric conditions in Washington,

D. C, for a period of approximately three years. Results of the same tests for a 6-year period are shown graphically in the appendix. Conclusions are for the conditions of test described.

E. U. Condon, Director.

[ill
Paints for Exterior Masonry Walls

by Clara Sentel

ABSTRACT

Four classes of masonry paints, cement-water, resin-emulsion, oil-base, and syntheticrubber, and one whitewash were applied to test wall specimens of new and used com- mon brick; cast concrete; stone-, cinder, and lightweight-aggregate-concrete block; and

wood frame with cement-asbestos shingles to determine the durability of such paints on masonry surfaces. Specimens, exposed to atmospheric conditions for approximately

3 years, were rated on weathering characteristics. Durability of the paints was deter- mined on the bases of type of paint used, type of surface coated, methods of application and curing, and conditions of casting and painting.

CONTENTS

Page Foreword II

I. Introduction 1

II. Materials 2

1. Paints - 2

(a) Cement-water paints 2

(b) Resin-emulsion paints 3

(c) Oil-base paints 4

(d) Synthetic-rubber paints 5

(e) Whitewash 5

2. Wall specimens 6

(a) General description 6

(b) New common brick 6

(c) Used common brick 6

(d) Cast concrete 6

(e) Stone-concrete block 6

(f) Cinder-concrete block 6

(g) Lightweight-aggregate-concrete block-_ 6

(h) Cement-asbestos shingles 6

III. Painting the wall specimens 6

1. General procedure 6

(a) Preparation of the surface 7

(b) Mixing of paints 7

(c) Application of paints 7

2. Cemen(>water paints 7

3. Resin-emulsion paints 7

4. Oil-base paints 7

5. Synthetic-rubber paints 7

6. Whitewash . 7 IV. Painting the field office 7

V. Test results 9

1. Basis of evaluation 9

(a) Appearance and durability 9

(b) General rating 9

(c) Reflectance 9

(d) Spreading rate 10

2. Paints 10

(a) Cement-water paints 11

(b) Resin-emulsion paints 11

(c) Oil-base paints 11

(d) Synthetic-rubber paints 14

(e) Whitewash 15

3. Wall specimens 15

(a) Performance of coatings on commonly

painted surfaces 15

(1) Stone-concrete block 15

(2) Cinder-concrete block 15

(3) New common brick 16

Page

(4) Lightweight - aggregate - concrete block 16

(5) Cast concrete 16

(b) Performance of coatings on surfaces not

usually painted 16

(1) Used common brick wall speci- mens 16

(2) New cement - asbestos shingle - faced wall specimens 17

VI. Summary and recommendations 17

VII. Appendix 19

I. INTRODUCTION

Tests to determine the comparative durability of four general types of paints and one whitewash applied under practical painting conditions to wall specimens of porous masonry

were conducted at the National Bureau of

Standards in an out-of-door test field. The specimens were exposed to weathering conditions for

periods of from 24 to 33 months during the

years from 1940 to 1943. As the use of porous

masonry products has increased, so has the

need for more knowledge of water-repellent and

decorative finishes for such surfaces..

Permeability of masonry walls to water has

been discussed in other reports of the Building

Materials and Structures series.' This paper

discusses the condition of specimens of porous

masonry after exposure to the weathering period and reports the behavior of coatings of vari- ous types which were applied to these speci- mens. Masonry specimens, to which the paints

herein discussed were applied, were constructed

of new and used common brick; cast concrete;

Building Matei'ials and Structures Reports BMS55, Effects of Wetting and Drying on the Permeability of Masonry Walls ; BMS76, Effect of Outdoor Exposure on the Water Permeability of Masonry Walls ; BMS82. Water Permeability of Walls Built of Masonry Units; BMS94. Water Permeability and Weathering Resistance of Stucco-Faced. Gunite-Faced, and "Knap Concrete-Unit"

Walls ; and BMS95, Tests of Cement-Water Paints and Other

Waterproofings for Unit-Masonry Walls.

[1]
stone-, cinder-, and lightweight-aggregate-concrete block ; and wood frame with cement-asbestos shingle facing.

Paints used in the tests were of the types

commonly applied to masonry surfaces. They

were white in color and included 20 cementwater paints, 4 resin-emulsion paints, 4 oil-base

paints, 5 synthetic-rubber paints, and 1 whitewash. Some were proprietary brands while

others were experimental mixes. These paints are suitable for use on foundations, exterior

walls, porches, and fences, but should not be

used for floors such as concrete, brick, or for

other surfaces which might be subject to abrasion. Instead, for such floors, a very harddrying paint with good water resistance and

good gloss retention is recommended.

The test field used for the masonry paint ex- periments discussed in this paper was located

in a section of the grounds of the National

Bureau of Standards which was exposed to sunlight during the greater portion of the day (see

fig. 1). Trees adjacent to the east and south

side of the test field shaded a few of the wall

specimens and tended to increase the humidity

of the area. It was found that toward even- ing appreciable condensation was observed on

the test panels. This condition was attributed

to the sudden drop in temperature caused by

the disappearance of the sun and was found

favorable for the curing of cement-water paints

but detrimental to oil-base and resin-emulsion

type paints.

In the same area as that in which the specimens were tested at the Bureau, a small field office was built to facilitate the recording of

test data and to serve as an "in-service" speci- men. Further details concerning the field office are given in chapter IV of this paper.

II. MATERIALS

1. Paints

(a) Cement-ivater Paints

Cement-water paints are water-dilutable

paints in which portland cement is the binder.

They are especiaUy suitable for use on porous

masonry walls that are damp at the time of

painting or are subject to dampness.

A typical cement-water paint film is hard,

strong, and relatively brittle. This property,

together with drying shrinkage, may result in

the development of fine checking, usually re- ferred to as "map cracking," (see chapter V).

Such paints should weather by erosion, that is, by gradual wearing away of the coating. This

behavior is considered normal, and unless ero- sion is rapid and map cracking progressive,

such a breakdown is not serious. Cement-water

paint possesses good decorative qualities as to hiding power and color. However, when wetted,

as by rain, it becomes somewhat translucent or darker in the case of a color. On drying, the

film returns to its original opaqueness and color. Cement-water paints vary widely in composition. The ratio of portland cement to other

ingredients is seldom less than 1 to 1, and may

be as high as 9 to 1 ; the usual average is about

3 to 1. In this study, 20 cement-water paints were

tested—6 proprietary brands and 14 experimental mixes. Proprietary brands were purchased in original containers. Experimental

mixes were made by tumbling the dry ingredients in a pebble mill (without pebbles in the

jar) for 24 hours. To prevent chemical changes

in composition, powder paints were stored in

moisture-proof containers.

Cement-water paints CW-1 to CW-5, inclusive, were proprietary brands. All had good

Figure 1.

A portion of the test field showing the position of the walls.

[2]
mixing properties and produced a smooth

finish. Composition of these paints, as determined by laboratory analysis, is shown in table

1.

Table 1.

Composition of proprietary brand cement- water paints CW-1 to CW-5

[Determined by laboratory analysis]

Table 2.

Composition of experimental mix cement- water paints CW-7 to CW-20

[Determined by laboratory analysis]

Paint

desig- nation

CW-1

CW-2

cw-s

CW-4

cw-.-j

Ingredients for cement-water paints

Portland cement : Titanium dioxide ! Insoluble

Salt (calculated as NaCl)

Stearates present

Portland cement

Calcium hydrated lime Hygroscopic salts and stearates present Portland cement

Insoluble (apparently mica'i Hygroscopic salts and stearatej present Portland cement

Titanium dioxide Lime

Insoluble

Salts and stearates pre ent Portland cement Lime

Zinc sulfide Insoluble . Salt and stearates pre ent

Composition

by weight

Percent 89

4

32

(') 48

49

(')

85

10

(')

75

5

710

(') 40

43

4

10

(')

'Amount not determined.

Cement-water paint, CW-6, was a proprietary material consisting of two parts—a powder and an oil-like sealer, which dried to a smooth finish. The powder was mixed with

water and applied to the damp surface; after

aging for 24 hours, the first coating was fol- lowed by the sealer. No analysis is available

since the material was supplied and handled

by the manufacturer's representative.

Cement-water paints CW-7 to CW-20, inclusive, were experimental formulas. The grout

and 100-percent portland-cement coats were mixed at the field, while the other paints were

prepared in the laboratory. Suflficient water was added to the dry ingredients to give a good brushing consistency. All the paints had

good mixing properties except the waterproofed, white cements, which are difficult to mix by hand but can be mixed readily in a mechanical agitator. Cement-water paints con- taining sand showed slight texture but those

without sand produced a smooth finish. Compositions of the cement-water paint group

CW-7 to CW-20 is given in table 2.

(b) Resin-emulsion Paints

Resin-emulsion paints are water-reducible

pastes of pigments ground in a vehicle of oil- extended resin (usually glycerol phthalate)

which has been treated with an emulsifying

agent to render it miscible with water. A typical resin-emulsion paint is easily applied by

brush or spray and dries within a few hours to

Paint

desig- nation

CW-7

CW-8

CW-9

CW-10

(grout)

cw-n

CW-1

2

CW-13

CW-1

4

CW-15

CW-1

6

CW-1

7

CW-18

CW-19

CW-20

Ingredients for cement-water paints

Portland cement

Calcium hydrated lime Portland cement Hydrated (92%) magnesium lime Portland cement

Portland cement Potomac River mortar sand (passing No, 20 sieve) •

Portland cement

Silica sand (passing No. 20 sieve) Calcium stearate Portland cement

Calcium stearate Portland cement

Calcium stearate Calcium chloride Portland cement

Silica sand (passing No. 20 sieve) Calcium chloride Lithopone (50% ZnS)

Portland cement

Calcium chloride Lithopone (50% ZnS) Commercial waterproofed white cement. _ Commercial waterproofed white cement-

_

Calcium chloride Portland cement

Calcium hydrated lime Calcium stearate Portland cement

Flake mica Calcium stearate Portland cement

Titanium dioxide Calcium chloride

Compo.sition by weight

Percent 70

30

70

30

100

50

50

5049

1

99

1

95

1446

46

4

4

924

4

100

50

49

1 98

1

1 93

34

a smooth, opaque, flat finish. This type of

paint normally weathers by chalking. However, excessive moisture or alkaline salt solutions forming back of the film may induce

blistering, followed by flaking, or the alkalies

may cause saponification of the nonvolatile vehicle resulting in erosion of the film.

Of the four resin-emulsion paints tested

RE-1, RE-2, and RE-4 were proprietary

brands while RE-3 was an experimental mix

made by a manufacturer of emulsified resins.

The compositions of these paints, shown in

table 3, were- supplied by the manufacturers.

All of the resin-emulsion paints, except

RE-2, mixed readily with water in the proportions of 2 parts paste to 1 part water (by

volume) for the first coat and 5 parts paste to 3 parts water for the finish coats. Brushing

properties were good and the emulsion did not

appear to break under the brush. Within 2

hours this paint dried dust free to a flat, smooth

finish suitable for recoating within 18 hours.

The paste for resin-emulsion paint, RE-2, was mixed in the proportions of 2 parts paste

to 1 part water (by volume) for both the first

[3]
Table 3.

Composition of resin-emulsion paints RE-1,

RE-2, RE-3, and RE-i"

Table 4.

Composition of oil-base paints 0-1, 02, 0-3,

0-V

Ingredients for resin-emulsion paints

Pigment: Titanium dioxide Titanium-barium pigment- Mica

Silica Vehicle: Emulsified alkyd resin Water

Pigment: Titanium dioxide Zinc oxide -_- Basic carbonate white lead -

.

Magnesium silicate Aluminum silicate Calcium carbonate

Vehicle: Water and volatile matter. _

,

Oil-extended synthetic resin_ Fungicide Emulsifying agents Pigment: Titanium dioxide Titanium-barium pigment Mica

Silica Vehicle: Emulsified resin (containing 50% solids) Pigment:

Lithopone

Vehicle: Resin emulsion (containing 50% soUds) _ Casein solution Lead manganese drier

Composition

by weight

Percent

1078

6

5050

16152728

6132

1

40

40

10

10

100

60

39

47

53

52

48

40

60

45

55

^Composition furnished by manufacturer. and finish coats. Brushing properties were

poor and the paint rolled under the brush.

Within 2 hours the film dried dust free to a

grainy, flat finish suitable for recoating within

18 hours.

Paint

desig- nation

0-^1

0-2

0-3''

0-4

Ingredients for oil-base paints

Pigment:

Lead-zinc pigment Titanium dioxide

Silica and silicates Vehicle: Processed linseed and tung oil- Mineral spirits Japan drier Pigment:

Portland cement

Tinting pigment

Vehicle: Linseed oil Drier Priming paint: Pigment: Titanium pigment , Carbonate lead Magnesium silicate Vehicle: Treated linseed and tung oil Drier and thinner

Finish coating: Pigment: Titanium pigment Lead sulfate Zinc oxide Magnesium silicate Vehicle: Linseed oil Drier and mineral spirits Pigment: White lead Zinc oxide Titanium oxide Magnesium silicate Vehicle: Linseed oil

{ Drier and thinner

Composition

by weight

Percent

78

220

59

26

15

92 to 50

8 to 50

71

23

94

6

38

3725

6040

37

16 29

1890

10

6026

35

03

37

61

39

65

35

'Composition furnished by the manufacturer.

"Oil-base paint, OS, consisted of two separately formulated paints, a primer and a finish coating.

(c) Oil-base Paints

The term "oil-base paints" is commonly used

to describe ready-mixed paints which contain

opaque pigments suspended in a vehicle of drying oils and thinner. Paints designed for use on masonry are usually formulated so that the

first coat seals the surface sufficiently to prevent "spotting" or "flashes" of the second coat. Two coats, as a rule, are necessary for good

hiding and durability.

Application of oil-base paints to damp surfaces or surfaces which may be subjected to dampness by the infiltration of moisture

through structural defects is not recommended.

The presence of such moisture frequently results in failure of the paint film by blistering,

flaking, or rapid erosion.

Four commercial oil-base paints 0-1, 0-2,

0-3, and 0-A were tested. The composition of

the proprietary brands in their reduced form

were supplied by the manufacturers and are shown in table 4. Oil-base paint, 0-1, thinned according to the

manufacturer's directions, showed good brushing qualities and penetration and no tendency

to sag. Within 6 hours the film dried dust free

to a smooth, eggshell finish suitable for recoat- ing within 24 hours.

Thinned according to the manufacturer's di- rections, oil-base paint, 0-2, had a slight pull

under the brush but showed good penetration.

Within 8 hours the film dried dust free to a smooth, glossy finish suitable for recoating

within 48 hours.

Oil-base paint (priming and finish), 0-3,

consisted of two separately formulated paints, a primer and a finish coating, therefore re- quired no thinner. Both showed good brushing

qualities and penetration and no tendency to sag. The primer showed good sealing properties and within 8 hours dried dust free to a smooth, semiglossy finish suitable for recoating

in 48 hours. The finish paint dried dust free

within 8 hours to a smooth, semiglossy finish

and to a firm finish in 24 hours.

Applied only to the specimens covered with

cement-asbestos shingles, oil-base paint, 0-4,

was an outside house paint thinned with spar

varnish (Fed. Spec. TT-V-121b) in the proportions of 2 qt of varnish per gal of paint for

the priming coat and 1 qt of varnish per gal

of paint for the finish coat. The priming coat dried dust free within 8 hours to a smooth, egg-

[4]
shell finish suitable for recoating within 24

hours. The finish coat dried to a smooth, high

eggshell finish in 24 hours. The paint had good

brushing and sealing properties.

(d) Synthetic-rubber Paints

There are two types of synthetic-rubber

paints: the rubber-solution type, in which the

synthetic rubber is added to a vehicle of treated

drying oils, aromatic hydrocarbons, and coal tar thinners; and the rubber-emulsion type, in

which the synthetic-rubber resin is treated

with an emulsifying agent so that the paste

paints are reducible with water. As these

paints usually contain less pigment than those

of other exterior finishes, the pigments selected

must produce films of high opacity in order to give adequate hiding in two coats. Coatings of synthetic-rubber paint should

weather by chalking, although complete weathering characteristics for coatings of this type

have not yet been fully established.

Five commercial brands of synthetic-rubber

paints, SR-1, SR-2, SR-3, SR-i, and SR-5, were tested. When the tests were made, rubber-emulsion paints had poor storage stability

and could only be supplied directly by the manufacturer. The composition of specimen SR-5

was not available. The compositions of the

other four rubber-emulsion brands were furnished by the manufacturer and are shown in

table 5.

Table 5.Composition of synthetic-rubber paints,

SR-1, SR-2, SR-3, and SR-i^

Paint

desig- nation

SR-1

SR-2

SR-S

SRIngredients for synthetic-rubber paints Materials by weight

I Pigment: Titanium dioxide Zinc oxide Magnesium sUicate Diatomaceous silica Vehicle: Rubber-base solution (containing 28% solids) _ Pigment:

Lithopone

Vehicle: Chlorinated rubberSolvent mix

Plasticizers Water

Pigment: Titanium dioxide

Vehicle: Chlorinated rubber.

Solvent mix

Plasticizers Water

Pigment: Titanium dioxide

Vehicle : Chlorinated rubber.

Solvent mix

Plasticizers Water

Percent

44

20

31

5

100

100

1837

1233

100

1837

1233

100

1738

1431

38

62

25

75

23

77

23

77

'Composition furnished by manufacturer. SR-1, synthetic-rubber paint, was of the rubber-solution type. Brushing properties and finish were good and were comparable to those of

oil paints formulated for use on masonry. The

material was used with satisfactory results as a primer under resin-emulsion and oil-base

paints and as a finishing material. For the

priming coat, rubber-solution type paint, SR-1,

mixed readily with turpentine in the proportions of 1 pt turpentine to 1 gal paint; the

finish coat was applied as received. Within 2

hours the film dried dust free to a smooth, lowgloss finish suitable for recoating within 18

hours.

Synthetic-rubber paints SR-2, SR-3, SR-4,

and SR-5 were the rubber-emulsion type and

had physical properties similar to those of the

resin-emulsion type.

Mixing readily with water in the proportions

of 4 parts paint to 1 part water (by volume),

synthetic-rubber paint, SR-2, is used for priming and finish coats. This paint had good brushing properties. Within 1 hour the film dried

dust free to a smooth, flat finish suitable for

recoating within 18 hours.

SR-3, synthetic-rubber paint, mixed readily

with water in the same proportions as rubberemulsion paint, SR-2, and showed good brushing properties. Within 1 hour the film dried

dust free to a smooth, flat flnish suitable for

recoating within 18 hours.

In the same proportions as SR-2, syntheticrubber paint SR-i mixed readily with water.

Brushing properties were fair and there was

slight pull under the brush. Within 1 hour

the film dried dust free to a smooth, flat finish

suitable for recoating within 18 hours.

Synthetic-rubber paint, SR-5, also mixed

readily with water in the same proportions as SR-2. Brushing properties were poor and the

paint rolled under the brush. Within 1 hour

the film dried dust free to a grainy, flat finish

suitable for recoating within 18 hours. The

composition of this paint was not available.

(e) Whitetvash

While the study of lime coatings was not anticipated in this project, one whitewash formulation was included. Whitewash is basically

lime (either hydrated or quicklime paste) and

water, but frequently other ingredients are added. The National Lime Association" lists ten formulas in its Bulletin No, 304-D. Formula No. 4, which was used in this test, con- tained the following ingredients

Casein 5 lb dissolved in 2 gal of hot water. Trisodium phospliate..3 lb dissolved in 1 gal of water. Formaldehyde 3 pt mixed in 3 gal of water. Lime paste 8 gal (50 lb of hydrated lime

mixed with 6 gal of water.)

When applied to damp walls, this whitewash

dried to an opaque, hard, dust-free finish. Dur-

=National Lime Association, 927 Fifteenth Street N.W., Washington 5, D.C.

[5]
ing rainy weather the film became somewhat

transparent but dried to its original opaqueness.

2. Wall Specimens

(a) Ge7teral Description

The wall test specimens were constructed to face north and south and to have a vertical ex- posure. With the exception of the cement-asbestos shingle-faced walls, all specimens had

faces measuring 2 ft by 2 ft with an over-all area of 11 sq ft, including both faces and sides.

The shingle-faced walls had an area of approximately 32 sq ft. A sheet of grade A asphalt roofing was

placed between the wall specimen and the base on which it rested, to serve as a "water break."

The wall specimen and the base were fastened

together by 4-in. bolts embedded in mortar.

Walls built of unit masonry had sloping roofs

of painted galvanized metal equipped with gutters for carrying water off to the side away

from the walls; the cement-asbestos walls had

sloping roofs with a slight overhang, covered

with painted asphalt roofing ; and the cast-concrete walls had flat tops painted with two coats of exterior masonry paint containing chlorinated rubber.

The mortar used in walls of masonry units

consisted of 1 part gray Portland cement, 1 part

calcium hydrated lime, and 6 parts Potomac

River mortar sand, by volume.

Commercial workmanship was specified*.

Joints were not completely filled with mortar.

Bed joints were furrowed, collar joints were

left open, and only the outside of head joints

was filled by lightly buttering outer edges of

the bricks. Joints were cut flush with faces of

specimens.

Wall specimens were allowed to stand from

one to six weeks before painting. The first specimens to be coated were painted with

cement-water or synthetic-rubber paints as they are usually less susceptible to moisture

and alkaline solutions within new walls than

are oil-base or resin-emulsion paints.

(b) Neiv Common Brick

Wall specimens for test purposes were con- structed with two grades of new red shale

brick, one more porous than the other and, in

each case, the walls were eight courses high.

In one series, five header brick were used for

the fifth course with header brick at alternate courses at the ends of the wall ; whereas, in the

other series, header brick were used only at alternate courses at the ends of the wall. Commercial workmanship was used.

(c) Used Common Brick

The material for a few walls was used com- mon brick, which was purchased from a wrecking concern. These brick were laid in the condition received, and no attempt was made to determine the kind, amount, or depth of stains.

(cl) Cast Concrete

The cast-concrete walls consisted of 1 part

cement, 2.2 parts sand, and 3.5 parts coarse aggregate (by volume) . The ingredients were mixed commercially and were cast in forms

made of smooth pine coated with form oil. Rather dense slabs were produced, but the sur- face was marred with voids apparently made

from entrapped air.

(e) Stone-concrete Block

The stone-concrete block were sand and

gravel block, gray-tan in color, with porous but

fairly smooth faces. Test walls constructed

with the block were similar in dimensions and

workmanship to those of the lightweight-aggregate-concrete or cinder-concrete block.

(f) Cinder-concrete Block

Cinder-concrete block were dark gray in

color and measured approximately 8 by 8 by 12

in. Walls were laid two blocks wide and three courses high. Joints were lightly smoothed

with the point of a trowel.

(g) Lightweight-aggregate-concrete Block

Expanded blast-furnace slag, medium gray

in color, was used for the lightweight-aggregate-concrete block. Each block measured approximately 8 by 8 by 12 in. and had two oval

cells. Walls were laid two blocks wide and

three courses high. Joints were lightly

smoothed with the point of a trowel.

(h) Cement-asbestos Shingles

The specimens for these tests were panels

consisting of 16 new, oyster-white, cement-asbestos shingles laid with an 11-in. exposure

over a wood frame. The shingles were purchased from two manufacturers in regular and

heavy thicknesses.

III. PAINTING THE WALL SPECIMENS

1. General Procedure

The methods of preparing the surface for

painting, and of thinning, mixing, and applying the paints were essentially the same for all materials tested.

The exact procedures followed in the application of each type of paint are described in succeeding sections of this chapter.

[6]
r

(a) Preparation of the Surface

Prior to painting, dust and loose mortar were removed by brushing with a stiff bristle brush.

During hot, dry weather very porous surfaces,

such as concrete block, were sprinkled with

water to decrease the suction and to prevent

the paint from setting under the brush, except

where oil-base paints were to be applied. To

remove the surface glaze, cast-concrete walls were washed with a 10-percent hydrochloric

acid solution and then thoroughly rinsed with

,; clean water.

(b) Mixing of Paints

Proprietary paints were mixed according to the manufacturers' direction, which conformed

! closely to the procedure used in mixing the ex- perimental paints. Thinner was added gradually to the mixture which was stirred conj stantly. Water was used for paints of the

1 cement-water, resin-emulsion, and rubberemulsion types. If the manufacturer indicated

that the mixture should be thinned, either paint

j thinner, mixing sealer, or spar varnish was

! added to the oil-base paints. Turpentine was

j used for thinning the first coat of rubber-soluI tion paints.

i In the preparation of experimental mixes for

j tests of cement-water paints, approximately

i| equal parts (by volume) of powdered cementi"i water paint and water were used. A small portion of the water was first stirred into the dry

I powder. As soon as a smooth paste had been

jj formed, the remainder of the water was added

i and the paint solution again mixed well. This was allowed to stand for thirty minutes before

being given another vigorous stirring, after

j: which the paint was ready for application to

1, the wall specimen panels.

(c) Application of Paints

All paints were applied by brush. Cementwater paints were worked well into the damp

walls with an ordinary scrub brush to fill voids

and openings and to provide a continuous,

water-resistant film. The use of soft-bristled or whitewash brushes is not recommended for

^ the application of cement-water coatings, as

] this method will not produce as good mechanI ical bond between the paint and the surface as

stiff-bristled brushes. A 3-in. paint brush was

employed to spread organic coatings on the

surfaces of the specimens and a whitewash

[ brush was used for whitewash.

' 2. Cement-water Paints

i Two coats of cement-water paints were applied to the specimen panels allowing 24 hours

! of drying time between coats. During hot, dry

weather the first coat was sprayed lightly with

water before application of the second coat,

which was kept damp for 72 hours. During

hot, windy weather the walls were sprayed late in the afternoon until the films were well dampened; during damp, humid weather no spraying was necessary. The films hardened satisfactorily in approximately 3 days.

3. Resin-emulsion Paints

For tests on resin-emulsion paints, surfaces

of the wall specimens were given two coats. The resin-emulsion paints were either self- primed or applied over cement-water or synthetic-rubber primers. If it rained during the

24-hour aging period of the resin-emulsion or synthetic-rubber primers, application of the

second coat was postponed until the first clear

day. Cement-water primers were allowed to age 72 hours.

4. Oil-base Paints

To obtain information on the behavior of oil- base paints, two coats were applied. The oil- base paints were either self-primed or applied over cement-water or synthetic-rubber primers.

Twenty-four hours of drying time elapsed after

the application of synthetic-rubber primers and

between two coats of oil paint. After a cementwater primer was used or before the oil-base

paint was applied directly to porous masonry,

at least 1 week of clear, dry weather was

allowed to precede application of the oil-base

coating.

5. Synthetic-rubber Paints

The surfaces for testing were given two coats

of synthetic-rubber paints. They were self- primed or applied over cement-water primers.

Twenty-four hours of drying time was allowed

between coats for synthetic-rubber primers and

72 hours for cement-water primers. Rubber

paints were applied on either clear or damp

days but not to surfaces on which there was

free water.

6. Whitewash

Two coats of whitewash were applied to the

test surfaces. The walls were dampened with

water before brushing on the first coat. Twenty-four hours of drying time was allowed

between each coat. The second coat of whitewash dried to a flat, opaque finish. A schedule which may be used as a guide in

estimating the drying time for various masonry

paints is given in table 6.

IV. PAINTING THE FIELD OFFICE

The small structure which served as a field office was built of 3-cell, 8- by 8- by 16-inch,

open-textured, cinder-concrete block laid up

with cement-lime mortar.

[7]
Both the exterior and interior walls were

finished with grout containing equal parts (by

volume) of white portland cement and Potomac

River mortar sand mixed with enough water to give a creamy consistency. The grout was

scrubbed into the exterior walls and allowed to harden for 24 hours, after which a second coat

consisting of 2 parts of white portland cement,

and 1 part of Potomac River mortar sand

mixed with enough water to give a creamy consistency was applied. The exterior grout finish

dried to form a light cream-colored, hard, dustfree surface, possessed of good decorative qualities and also provided an efficient barrier

against rain penetration. After exposure of

slightly more than one year, the grout was

clean, nonchalking, and relatively free of map

cracking as is shown in the illustration of the

field office, figure 2. For the interior walls, a first coat of grout

was scrubbed into the faces and allowed to age

for 96 hours. A coat of resin-emulsion paint was then applied which dried to a smooth, flat finish in 24 hours.

In order to obtain additional information on

synthetic-rubber solution paint in service, however, two coats were applied over the grout

finish on the exterior walls and chimney. The

rubber-base paint was easily applied, had good

covering and hiding properties, and was given

a descriptive rating of "Very Good" or a numerical rating of 9 after 2 years of exposure.

Table 6.Time to be allowed between applicatioyis of typical masonry ^oaints on concrete and clay surfaces

Wall specimens Grout Cement water Resin emulsion Oil base Rubber solution Whitewash

1st coat Drying

time

2d coat Drying

time

1 "t coat Drying

time

2d coat Drying

time

1st coat Drying

time

2d coat Drying

time

1st coat Drying

time

2d coat Drying

time

1st coat Drying

time

2d coat Drying

time

1st coat Drying

time

2(i coSit Drying

Stone-concrete block Days

\

1 30

90

3

Days

1 Days Days Days Days Days Days Days Days Davi Davt Do 1 Do 1 1 Do 2 2 Do 1 I Do I 30'

90'

3'

1 Do 1 1 Do 2 2 Do 1 1 Do \ I

Cinder-concrete block 1

1 3090

3

1 Do 1 Do --r 1 Do 2 2 Do 1 1 Do I 30

90

3

1 Do 1 1 Do 2 2 Do 1 1 Do 1 1 Lightweight aggregate concrete block Do

1

1 30

90

3

1

1 Do 1 Do__. 2 2 Do 1 1 Do 1 30

90

3

1 Do 1 Do 2 2 Do 1 1 Do 1 1 New common brick ' - 1 3090

3

1 Do 1 Do 2 2 Do i 1 Do 1 Do 2 2 Do 1 1 Do 1 1 Cast concrete _ 1 1 Do 1 Do 2 2 Do 1 1 Do 1 1 Cement-asbestos shingle _ _ 1 Do 2 2 Do 1

1

1

1

1

1

Used common brick:' Sound, with tight joints. _ Chipped or with open joints Do

3

1 1

^If 2 coats of cement-water paint are necessary, the second coat may be applied 24 hr. after the iirst coat. The second coat should then be allowed to dry for 30 days before application of the resin-emulsion paint, 90 days before application of oil-base paint, and 3 days

before rubber solution paint. ^Grout would not ordinarily be used on new common brick walls, but may be if necessary, following the same procedure as is given

for concrete block walls. ^Unstained used common brick can be treated same as new common brick.

[8]
Figure 2.

Field office with cinder-concrete block walls and chimney of new common brick.

V. TEST RESULTS

1. Basis of Evaluation

To evaluate the performance of the coatings

included in this report, the paints were applied

to the surfaces and allowed to age, after which

they were rated for appearance, durability, and

general performance. The spreading rate and

the reflectance of each separate coat of paint were also noted. Wall sections constructed of

new common brick; cast concrete; stone-, cinder-, and lightweight-aggregate-concrete block were rated according to the paint used. However, because badly stained used common brick

and new cement-asbestos shingles would not or- dinarily be painted, the only basis by which

their paint performance could be evaluated was

according to the coating surface.

(a) Appearance and Durability

The appearance and durability of the paints were classified descriptively as: "Very Good,"

"Good," "Fair," "Poor," and "Very Poor" and

numerically as "9-8," "7-6," "5-4," "3-2," and

"1-0." The number of wall specimens in each

classification was tabulated for each paint

tested.

(b) General Rating

The general rating was an arbitrarily devised means of evaluating the performance of

each paint. The rating scale was based on

weathering characteristics of the paint film,

which included the most common types of paint

failures described as "slight," "definite," and

"bad" and further defined as follows

Bleeding: The working up of a stain or other

material into succeeding coats, imparting to them a certain amount of color. Blistering : Formation of bubbles on the sur- face of paint film, usually caused by moisture

behind the film. Chalking: Powdering of the paint film at or just beneath the surface.

Checking: A defect in organic coatings, manifested by slight breaks in the film surface.

Erosion: Wearing away of the paint film by

the action of the weather.

Flaking: Detachment of small pieces of coatings, generally irregular in shape, and having an average diameter of less than i^. in. (See

Scaling.)

Map cracking: Slight breaks in the film sur- face of cement-water paints.

Scaling: An advanced form of flaking; arbitrarily called "scaling" when the detached

pieces of coating have an average diameter

greater than i/i in. (See Flaking)

Weathering characteristics of cement-water

paints and organic coatings (resin-emulsion,

oil-base, and synthetic-rubber paints) were

classified according to the following scale of

descriptive terms and numerical values:

Very good (9-8) : Cement-water paints—no

evidence of deterioration. Organic coatings

slight chalking. Though they were equally as durable as the organic coatings, cement-water

paints were less decorative because of stains

and collection of dirt.

Good (7-6): Cement-water paints—slight

map cracking and erosion. Organic coatings

slight chalking. (Repainting not necessary for

protection, but would improve appearance. Surface should be prepared by light brushing.)

Fair (5-4-) : Cement-water paints—bad map

cracking, slight scaling, erosion partially ex- posing surface. Organic coatings—definite

chalking, slight checking and flaking. (Repainting advisable. Loose, scaling paint should be

removed by brushing.)

Poor (3-2): Cement-water paints—definite,

erosion, bad scaling. Organic coatings—film

breakdown (checking, cracking, scaling.) (Repainting indicated for protection and appearance. Surface should be well cleaned with a

wire brush.)

Very Poor (1-0): Cement-water paints—bad

scaling, bad erosion. Organic coatings—flak- ing and bad erosion. (Repainting indicated.

Surfaces should be well cleaned with a wire

brush.)

(c) Reflectance

Reflectance readings, by indicating color

changes in painted surfaces, were one means

of evaluating hiding power of paints, appeai'- ance during weathering tests, amount of dirt

[9]
collected by the film, and degree of erosion. In

these tests, readings were made before the sur- faces were painted, as soon as the paint was

dry, and at intervals during the tests. Reflectance of surfaces ranged from 2 percent for

cinder block to 35 percent for concrete surfaces. Initial reflectance readings were listed

for each type of paint to show the degree of

hiding obtained when two coats were applied to the various masonry surfaces. Subsequent

readings were not reported numerically but

aided partially in determining composite properties of the paints.

(d) Spreading Rate

Spreading rate is the area covered by coat- ing a surface with a given quantity of paint;

it is expressed in square feet per pound of dry

powder for the cement-water paints and square

feet per gallon of mixed paint for the organic

coatings. For instance, 1 pound of cementwater paint should cover approximately 25

square feet on cast concrete and 1 gallon of

organic coating should cover approximately

400 square feet on brick or similar surfaces.

2. Paints

(a) Cement-ivater Paints

Cement-water paints as a group were satisfactory both in appearance and durability, re- ceiving a general rating of 70 percent "Good",

Figure 3.

Specimen of new common brick painted

with two coats of commercial cement-ivater paint.

Figure 4.

Cast-concrete specimen painted with two

coats of cement-water paint. Dark streaks on the upper portion of the panel were caused by

dirt washing from the flat top.

20 percent "Fair", 5 percent "Poor", and 5 percent "Very Poor." The high rating shown is a good indication that this type of paint is suitable for use on new porous masonry. Fig- ure 3 illustrates a typical cement-water paint

after 3 years exposure.

As indicated by their average ratings, most

of the cement-water paint films weathered by

erosion and map cracking. Erosion was more

pronounced on the cast-concrete walls and was

probably caused by the dense and uneven sur- face and the flat tops, which permitted water

to run down over the face of the specimen.

Voids and unevenness of the concrete are illus- trated by the form marks and depressions

shown on the panel in figure 4. Poor adhesion,

indicated by flaking and scaling of the film, was noticed on new common brick coated with

cement-water paints designated, CW-2 and

CW-6. This is shown in figure 5 where definite

flaking has occurred on the bottom course and

slight flaking over a scattered area. Cementwater test paint, CW-2, however, appeared to adhere satisfactorily when applied to open-textured surfaces such as cinder- and stone-concrete block. As a class, cement-water paints

had a tendency to give best results on opentextured walls. Test results are shown in table

7.

[10]
(b) Resin-emulsion Paints

Resin-emulsion paints as a group received a

general rating of 29 percent "Good," 42 percent

"Fair," 24 percent "Poor," and 5 percent "Very

Poor." The wide range of general ratings,

which resulted in comparatively low average

ratings, could be attributed to differences in the

priming coats. When applied over a base coat

of grout or a cement-water paint containing

little or no lime, resin-emulsion paints weathered by chalking and gradual erosion. Figure

6 shows typical resin-emulsion paint applied on new common brick over grout. Figure 7 shows

the same paint applied on stone-concrete block over a portland cement base. When applied

directly to new masonry, these coatings failed

by blistering and flaking except where the paint

film was sufficiently porous to allow the moisture to pass through. This type of failure is well illustrated in figure 8 by the dark areas which show where the paint has flaked from

the brick.

Test results indicated that for satisfactory use of resin-emulsion paints on new open-textured masonry, particular attention should be

given to selecting a primer which will fill the

voids and protect the finish coat from excess

alkali which normally "leaches" from new

walls. Results are shown in table 8.

(c) Oil-base Paints

Oil-base paints did not follow a prescribed

pattern, but as a group received a general rat- ing of 40 percent "Good" and 60 percent

"Fair." The variation in performance of the same paints used on the same type of surface' can be attributed to the application or omission

of a protective first coat. Open-textured wall

specimens primed with a grout coating which was allowed to dry and followed by two coats

of oil-base paint showed less flaking, scaling,

and bad erosion than those covered only by the

oil-base coatings. Figure 9 shows the even tex- ture and good appearance of two coats of oilTable 7.

Test results of cement-water paints

Paint

desig- nation

Number

of test walls

Wall specimens Spreading rate (average)

Initial

reflec- tance

Appearance Durability General

rating

(average) Material Primer Finish coat VG G F P VP VG G F P VP

CW-1 8 New common brick; stone-concrete

block; cinder-concrete block;

cast concrete.

sg ft/lb sq ft/lb Percent

22 39 79 5 2 1 1 5 2 7 CW-2 8 Do 25 42 81 2 3 3 1 1 6 3 CW-S 4 New common brick; stone-concrete

block; cinder-concrete block. 18 32 75 3 1 4 CW-4 5 New common brick ; stone-concrete

block; cinder-concrete block;

cast concrete. 25 40 78 3 2 4 1 G CW-5 5 Do 25 40 81 2 2 1 2 2 1 5 CW-6 3 New common brick; east concrete; lightweight - aggregate-concrete

block. (>) () 73 3 3 1 CW'7 4 New common brick; stone-concrete

block; cinder-concrete block. 23 37 81 3 1 4 7 CW-8 3 Do 19 32 80 2 1 3 7 CW-9 6 New common brick; stone-concrete

block; cinder-concrete block;

cast concrete. 19 34 80 5 1 5 1 7 CW-10 1 Cinder-concrete block. 10 18 70 1 1 7

(Grout) CW-11 3 New common brick; cast concrete; lightweight - aggregate - concrete

block. 22 32 78 1 1 2 1 5 CW-12Z... 3 Do 23 32 78 1 1 1 2 5 CW-13 3 Do 28 33 78 1 1 3 0 CTF-/4 3 Do 24 33 79 1 1 3 G CW-15 3 Do 24 31 79 2 2 1

3 Do 24 31 79 2 1 2 1 G CW-1 7 3 Do 26 33 79 2 1 3 CW-18 3 Do 27 37 81 2 1 2 1 6 CW~I9 3 Do 26 36 79 2 1 3 CW-20 3 Do 26 35 80 2 1 2 1 G

j 'Sorayed on by manufacturer's representative.

[11]
Figure 7.

Resin-emulsion paint, RE-1, applied over

Portland cement wash to stone-concrete block.

Figure 5.

Commercial cement-water paint applied to specimen of new common brick.

Poor adhesion is indicated by the flaking and scaling shown in the dark areas in the photograph.

'w—

r

Figure G.Resin-emulsion paint, RE-1, applied over grout on new common brick.

base paint applied over grout on cinder-concrete block. Figure 10 shows the first stage of

flaking and scaling which may occur when oil- base paints are applied directly to open-textured masonry. On wall surfaces known to be damp, a primer of rubber-solution paint improved the durability of the finish coat. The results obtained in tests of oil-base

paints, indicate that they should not be used

Figure 8.

Specimen, of new common brick to which

two coats of resin-emulsion paint, RE-1 , ivere apjilied

directly. The dark areas show where the paint has flaked and scaled from the brick.

on open-textured masonry surfaces, either old or new, unless a grout or similar coating has

first been applied to fill the openings. As oil- base paints produce films which are generally

impermeable to moisture, their use is seldom

recommended on masonry walls less than 6

months old. The results of tests on three oil- base paints are shown in table 9.

[12]
Table 8.

Test results of resin-emulsion paints

Paint

desig- Numberof test

Wall specimens Spreading rate (Average) Initial

reflec- Appearance Durability General

rating

nation walls Material Primer 2d coat 3d coat tance VG G F P VP VG G F P VP Range

Average

RE-1.. 22 New common brick: stone- concrete block; cinder- concrete block; cast concrete.

sq ft/gal 279

sg ft/gal

1 384

)

sq ft/gal

«538

Percent

80 10 8 4 5 12 3 2 0 to 7 4

'19

RE-2.. 6 New common brick; stone- concrete block; cinder- concrete block; cast concrete.

375

1 429 '500 65 3 3 1 3 2 3 to 6 4i '16

RES.. 5 New common brick; light- weight - aggregate - concrete block.1 222

1 282 '325 80 3 2 2 2 1 2 to 7 5 ''18

RE-4.. 5 New common brick; cinder- concrete block; cast concrete.1 338

1 411 75 4 1 2 1 2 3 to 6 4

'17

'The spreading rate for wall panels primed with cement-water paints is expressed in sq ft/lb instead of sq ft/gal. ^Two specimens only. ^One specimen only.

Table 9.Test results of oil-base paints

Paint

desig- nation

Number

of test walls

Wall specimens Spreading rate (Average)Initial

reflec- tance

Appearance Durability General

rating

Material Primer 2d coat 3d coat VG G F P VP VG G F P VP Range

Average

S3 ft/gal sg ft/gal sg ft/gal Percent 0-1 12 New common brick; stone- concrete block; cast concrete; cinder-concrete

block.

191

'15 1 330 281 78 6 3 1 2 6 2 1 3 2 to 9 6

0-2 6 New common brick; stone- concrete block; cinder- concrete block; light- weight - aggregate - concrete block.

263

1 323 233 73 1 1 3 1 2 1 3 2 to 7 4

'14

OS 4 New common brick; cinder- concrete block; light- weight - aggregate - concrete block.

215

1 301 408 75 2 2 3 1 2 to 7 5

'15

'The spreading rate for wall panels primed with cement-water paints is expressd in sq ft/lb instead of sq ft/gal.

Table 10.Test results of synthetic-rubber paints, solution and emulsion types

Paint

desig- nation

Number

of test walls

Wall specimens Spreading rate (Average)Initial

reflec- tance

Appearance Durability General

rating Material Primer 2d coat 3d coat VG G F P VP VG G F P VP (Average)

SR-1... 5 New common brick; cinder- concrete block; cast concrete.

sg ft/gal

] 296

sqft/gal

1 340

sqft/gal 2375Percent 80 1 2 2 1 2 2 6

'14

SRS..^ 2 Cinder-concrete block; cast concrete.

\ 220

J 318 2310 78 1 1 2 5

/ UO

SRS... 4 New common brick ; cinder- concrete block; cast concrete; lightweight-aggre- gate-concrete block.

220

'16 1 326 »295 78 2 1 1 1 1 2 3

SR-4--- 3 New common brick; light- weight-aggregate-concrete

block.

1 200

1 240 '293 76 2 1 1 2 3

'17

SRS.^. 2 Do ] 190 } 233 '290 74 1 1 2 3

' '16

'The spreading rate for wall panels primed with cement-water paints is exppressed in sq ft/lb instead of sq ft/gal. "One specimen only. *Two specimens only.

[13]
Figured.—Specimen of cinder-concrete- block painted

with oil paint over base coat of gro^it.

(cl) Synthetic-rubber Paints

The SR-1 synthetic-rubber solution-type

paint, of which there was only one sample, gave

satisfactory performance both for appearance

and durability, and a general rating of "Good".

Synthetic-rubber emulsion-type paints, SR-2,

SR-3, SR-i, and SR-5, were not as good, approximately 20 percent of their general ratings

being "Fair" and 80 percent "Poor". It may

be that a part of their failure can be attributed

to the fact that they were in an early stage of

development and formulation had not been perfected. Test results are shown in table 10. Figure 11 shows two coats of rubber-solution

type paint applied to a specimen constructed

of new common brick. The mortar joints in

the test specimen were purposely left open so that water, such as wind-driven rain, could

enter the wall. In some types of organic coat- ings this condition would normally cause early

breakdown by blistering and flaking. With

this sample of rubber-solution type paint, however, the effect observed after 30 months of ex- posure, other than the expected chalking, was

that slight flaking occurred on two bricks, as indicated by the small dark spots on the end

bricks in the 4th and 7th courses at the right

of the illustration.

Figure 10.

Open-textured stone-concrete block speci- men to ivhich two coats of oil-base paint were applied

directly.

Figure 11.

Specimen of new common brick to which

two coats of rubber-base solution-type paint were

applied directly.

[14]
Figure 12.

New common brick specimen painted with two coats of rubber-emulsion paint.

Figure 12 shows the film breakdown which

occurred when two coats of rubber-emulsion

type paint were applied directly to a wall specimen of new common brick. The coating first broke into small flakes and then eroded to the

extent that some of the bricks are completely

exposed,

(e) Whitewash

Whitewash was applied to three wall specimens, one each of new common brick, stone- concrete block, and cinder-concrete block. The

specimens weathered by definite erosion, slight

to definite scaling, and slight flaking, and re- ceived an average general rating of "Fair" or

a numerical rating of 4. All specimens were

rated "Fair" on appearance while two were'

rated "Fair" and one "Poor" or numerically

4 and 3 on durability. The spreading rate of

whitewash averaged 209 sq ft/gal for the first coat and 320 sq ft/gal for the second or finish

coat. Initial reflectance readings were 82 percent. No table is given for the results of tests of whitewash because of the small number of

tests made, and no photographs were taken of

these specimens.

3. Wall Specimens

Wall specimens were rated on two bases of

evaluation: Performance of coatings on com- monly painted wall surfaces and performance

of coatings on wall surfaces not usually

painted. Stone- and cinder-concrete block, new

common brick, lightweight-aggregate-concretc

block, and cast concrete were rated in the order

named on the basis of paint performance or general serviceability of the paint. This in- cluded the coverage, hiding power, color retention, and weathering properties of the coatings.

New cement-asbestos shingles and badly

stained used common brick are not usually

painted, therefore, in the rating for these few

specimens consideration was given to the painting surface as well as to the paint performance.

(a) Performance of Coatings on Commonly

Painted Surfaces

(1) Stone-concrete Block

Stone-concrete block wall specimens rated

first as a painting surface for all types of paints

including cement-water, resin-emulsion, oil- base, synthetic rubber, and whitewash. The

block used for these tests were of uniform, open

texture, light in color, and free of foreign substances such as iron particles which might

cause disintegration or staining.

For a durable and decorative coating on exterior walls of stone-concrete block, cementwater paints may be used. Synthetic-rubber or resin-emulsion paints applied to stone-concrete

surfaces give adequate performance when

brushed or sprayed directly on the block, but

much better results are obtained if a grout or cement-water paint is used as a base coat. For

satisfactory performance of an oil-base paint,

voids in the block must first be filled with

cement-water paint or grout. Whitewash applied directly on the block will give reasonable

serviceability.

(2) Cinder-concrete Block

Provided the cinder-concrete block is first given a grout coat, it may be satisfactorily

coated with either cement-water paints or or- ganic finishes.

Cement-water paints prove durable when applied directly to cinder-concrete block, but they

may have poor decorative properties if the

block to which they have been applied contains

small particles of iron. Wind-driven rain penetrating the block will corrode these particles

of iron causing them to "bleed" through the

coating. This mars the appearance of the surface, although it does not necessarily impair

its wearing properties. Application of a first coat of grout helps to correct such a condition

by filling the cracks and voids, making the block

less permeable to moisture. For block manufactured from magnetically cleaned cinders,

this condition does not exist and therefore two

coats of cement-water paint will be adequate

to provide a finish that is both protective and

decorative.

[15]
Open-textured block, such as the unvibrated

type, requires a base coat of grout prior to the use of an organic paint. This type of paint

spans but will not fill voids and allows the paint

film to break on aging thus leaving openings

through which moisture can enter. The grout

base should dry for approximately 3 months before applying the oil-base paint, 1 month before

applying the resin-emulsion finish, and 3 days

before applying the rubber-solution type of

paint.

(3) Neiu Common Brick

For open-textured walls, such as new com- mon brick, Portland cement-water paints are a durable and decorative coating. Tests indicate

that the Portland cement content of cementwater paints should be more than 50 percent by

weight. On walls where the mortar joints have

appreciable voids, a grout should be used or sharp sand should be incorporated in the first coat of cement-water paint. Oil-base or resinemulsion paints may be used with excellent re- sults over these coatings, provided adequate

time is allowed for the base coat to thoroughly

dry (approximately 3 months). Rubber-solution paint may be applied over the cementwater or grout base as soon as the base coat has

cured (approximately 72 hours).

Resin-emulsion or rubber-solution paints

may be applied directly to walls having tight

mortar joints. In the case of oil-base paints,

the walls should be allowed to age at least 6

months before the paint is applied.

(A) Lightweight-aggregate-concrete Block

Lightweight-aggregate-concrete block were

similar in appearance and texture to stone-concrete block and the performance of paints applied to these surfaces was much the same, ex- cept for the aggregate block which were coated

with rubber-emulsion paint. These paints gave

relatively poor performance and, because there was a greater number in proportion of these

specimens, the average rating for this group

was lowered.

(5) Cast Concrete

The surface of cast-concrete block was rather

dense and relatively smooth except for potmarks from air bubbles in the concrete, as shown in figure 4. The cement-water paint film on these surfaces was thin. Because the tops

of the block were flat, water ran over the block

faces, staining the paint on them with dirt and

increasing the rate of erosion.

Oil-base and rubber-solution coatings gave a continuous film over the cast-concrete surfaces

which did not readily absorb stain and which

on weathering chalked sufiiciently to be self- cleaning.

The rate of the resin-emulsion group of

paints fell between that of the cement-water

and the oil-base paints. They had better decorative properties than the cement-water paints,

but their porous films were likely to stain and

were subject to erosion.

(b) Performance of Coatings on Surfaces not

Usually Painted

(1) Used Common Brick Wall Specimens

The brick used for these tests was badly

stained and therefore required special surface

preparation which included vigorous wire

brushing and in most cases the application of a grout.

The paints which had good sealing properties gave satisfactory results. As these paints are relatively expensive, and as a great amount

of paint was required to adequately seal the un- even surface of the brick, a grout coat was applied. The grout coat produced a more even- textured surface and used less of the more

costly materials.

Oil-base and rubber-solution paints as well as resin-emulsion paints applied over a primer

gave satisfactory results and, as could be expected, the cement-water paint was poor.

Figure 13 shows the effective sealing properties of two coats of rubber-solution paint on

used common brick. On this specimen, a grout

coat was first scrubbed on to give a more even

Figure 13.

Specimeti of used common brick to which

two coats of rubber-base solution-type paint were

applied over grout.

[16]
Figure 14.

Specimen of used common brick to which

two coats of cement-water paint were applied

directly.

Scaling and staining of paint film are shown.

surface after which two coats of rubber-solution type paint were applied. With the exception of slight scaling on the lower edge of the

first course, this paint coating was in very good

condition after 30 months of exposure. There

was ho indication of staining or lack of adhesion as was observed when a similar stained

surface was coated with a porous paint.

Figure 14 shows the inadvisability of using

cement-water paint on badly stained used com- mon brick. The darker areas illustrate where

the paint failed to bond with the foreign material on the brick and the gray areas are brown discolorations which penetrated through

the cement-water coating from the brick surface. The few light areas show satisfactory

bonding and the absence of bleeding or staining indicating that the surface of the brick so covered was suitable for this type of paint.

These results may be of value in painting

stained chimneys, garage walls, and similar

surfaces. No table is given for results of tests of used common brick wall specimens.

(2) Neiv Cement-ashestos Shingle-faced Wall

Specimens

The cement-asbestos shingles used as facing on the wall specimens were new. Normally,

such shingles would not be painted until after

they had weathered. At the time the project was started, however, they were the only

shingles available, and it was belived that in- formation on the performance of paints applied

to these shingles might be helpful.

As illustrated in figure 15, the shingles offered an excellent painting surface in that their

refiectance was approximately the same as the

paints, the surfaces were of uniform porosity,

and the joints were so constructed that water

could not infiltrate behind the paint film. Two coats of rubber-solution paint gave excellent hiding and good durability.

For a primer, one coat of this paint proved

satisfactory under oil-base or resin-emulsion

paint.

Good results were also obtained by applying

two coats of either oil-base or resin-emulsion

paints. In fact, any organic paint designed

for use on masonry is satisfactory for application on shingles.

At the end of the test period the paint coat- ings were very satisfactory both in appearance

and durability, the only evidence of breakdown

being chalking and slight erosion.

Because cement-water paints do not contain an organic binder, they are not suitable as a

coating for new cement-asbestos shingles and

therefore were not applied to this group of wall

specimens. Test results are given in table 11.

VI. SUMMARY AND RECOMMENDATIONS

Considering the physical properties of the

various structures and the number of coats of

paint applied, cement-water paints as a class

•

-- —

\

1

i

' 1

J

Figure 15.

Cement-asbestos shingle ivall specimen to which two coats of rubber-base solution-type paint were applied,

[17]
give best results with oil-base, resin-emulsion,

and synthetic rubber-base paints following in

that order.

The masonry wall specimens rated as fol- lows: (1) New cement-asbestos shingle-faced

wall specimens, (2) stone-concrete block, (3)

cinder-concrete block, (4) new common brick,

(5) lightweight-aggregate-concrete block, (6) cast concrete, and (7) used common brick wall

specimens.

Cement-water paints are a decorative and

durable coating on exterior walls. The, method

of applying and curing cement-water paints

and the conditions under which painting is done are more important than the composition

of the paints, but the portland cement content

should not be less than 65 percent by weight

of the total paint.

The use of sharp sand in cement-water paint

or a priming coat of grout improves the durability of subsequent organic coatings on opentextured walls or those having cracks or other

defects.

Ordinary white portland cement or admixtures of cement and lime also give good results.

For improved decorative value, the cement

coating can be painted with an exterior masonry oil-base, resin-emulsion, or rubber-solution paint.

Cement-water paints should be used for the

initial painting of new masonry with the possible exception of cast concrete poured against

oiled forms. Further coatings are not necessary, but can be used if desired. A synthetic

rubber paint can be applied immediately after

the cement-water paint dries, but it is recom- mended that the cement-water paint age for at least 2 weeks before application of resin-emulsion paints and 3 months before the application

of oil-base paints.

Resin-emulsion paints have good decorative

qualities and are durable on exterior masonry

walls. For open-textured surfaces and brick

walls having cracks around the mortar joints,

the surface should be treated with a base coat

of grout or cement-water paint containing

sharp sand before resin-emulsion paint is applied. Resin-emulsion paints have good hiding

power and are easy to apply by brush or spray

to damp or dry walls. New masonry walls

should be allowed to age for at least 8 weeks

before painting.

Oil-base paints can be used on open-textured

masonry surfaces that have been treated to prevent infiltration of moisture or on close-textured masonry. Both should be allowed to age

for a period of from 6 to 12 months before

painting. It is essential that walls be dry at the time of painting and be so constructed or

so treated as to remain dry after painting. If these coatings are applied to a wet wall or one

that becomes wet through structural defects,

early failure by scaling and flaking may occur. Oil-base paints have good serviceability and

weather by chalking. This property tends to make them self-cleaning and lessens their ten- dency to be discolored by dirt and stain.

A grout composed of portland cement and

sharp sand is recommended as a base coat on

open-textured surfaces such as stone- and cinder-concrete block, lightweight-aggregate-concrete block, and new and used common brick

with joints which have not been tooled. The

grout should be allowed to age at least 90 days.

It may be applied immediately upon erection of

the wall or at any time during the aging period

of from 6 to 12 months.

If there is a possibility that the wall is damp

or contains soluble salts, a protective primer,

such as rubber-solution paint, should be used

as a first coat over the grout. In this case, one

coat of the oil-base paint should be sufficient to give a good finish. Two coats, however, will

give greater durability.

Synthetic-rubber paints may be applied to either dry or slightly damp wall surfaces but

should not be used on wet surfaces as excessive

moisture may prevent adequate bond. These

paints are of two types, rubber-emulsion and

rubber-solution.

The samples of rubber-emulsion paint were

received directly from the manufacturer and

represented experimental studies rather than

commercial products available for over-thecounter sales. The rubber-solution type is similar in composition to an oil paint except that a rubber

resin is used in the vehicle in place of synthetic or natural resin. It may be brushed or sprayed

and can be used either as a protective primer

Table 11.

Test results of paints on cement-asbestos shingle-faced wall specimens

Wall

specimens

Number

of test walls Paint

designation

Spreading rate (Average)

Initial

reflec- tance

(Average)

Appearance Durability General

rating (Average) Primer Finish coat VG G F P VP VG G F P VP

CA-/... - 4

4

2

3

SR-1; 0-1; 0-4: unpainted. SR-l; 0-1 : 0-4; unpainted.

Surface treated at the factory. SR-3; SR-1; 0-1.

sqfl/lb 213

218

sq ft/lh 302 320

Percent76

76

7778

44

2

3

2

2

2

1

2

2 S

3

7

CA-2 CA-3

CA-4 227 338 1 1

[18]
under oil-base or resin-emulsion paint or as a complete paint system. Two coats give adequate hiding and good durability. On opentextured surfaces, cement-sand grout should be

used and allowed to dry from 3 to 6 days. Rubber-solution paint is particularly suitable for

application on cement-asbestos shingles or siding, but will give good service on other masonry

surfaces.

Grateful acknowledgment for technical as- sistance in the preparation of this report is made to Eugene F. Hickson, Chief of the Paint

Section, and Edward J. Schell of the Building

Practices and Specifications Section of the National Bureau of Standards and to Louise D. C. Nobel and Edith R. Meggers of the same sec- tion for their painstaking effort in reviewing

this publication.

APPENDIX

The graph in this appendix presents the re- sults of investigations of some of the same

masonry surface coatings which were discussed

in the body of this report except that the specimens were subjected to out-of-door weathering

conditions for a total of 6 years instead of

three. The graph does not include exposure

data for as many test specimens as the main

part of the report because a portion of the test

field was dismantled to make room for activities in connection with the war effort, but a

sufficient number of specimens remained to give the representative performance of these

masonry paints and to substantiate the indications shown by the 3-year atmospheric exposure tests.

Surface --

CQ O OQ Oa O <0 QQ u u ^<0 OQ O <0 OQ

Cement Wafer Resin Emulsion Oil Base ' Rubber Base

Paints for Exterior Masonry Walls

Concrete blocks were made from sfone,cinder,ond lightweight aggregates.

Figure 16.Results of 6-year atmospheric exposure tests of paints for exterior masonry walls.

Washington, June 13, 1947. U. S. GOVERNMENT PRINTING OFFICE: 1947—748523

[19]



BUILDING MATERIALS AND STRUCTURES REPORTS

[Continued from cover page li] BMS32 Structural Properties of Two Brick-Concrete-Block Wall Constructions and a Concrete-Block Wall Construction Sponsored by the National Concrete Masonry

Association 15^ BMS33 Plastic Calking Materials 15^ BMS34 Performance Test of Floor Coverings for Use in Low-Cost Housing: Part 1 BMS35 Stability of Sheathing Papers as Determined by Accelerated Aging * BMS36 Structural Properties of Wood-Frame Wall, Partition, Floor, and Roof Constructions with "Red Stripe" Lath Sponsored by The Weston Paper and Manufacturing Co « 104 BMS37 Structural Properties of "Palisade Homes" Constructions for Walls, Partitions,

and Floors, Sponsored by Palisade Homes * BMS38 Structural Properties of Two "Dunstone" Wall Constructions Sponsored by the W. E. Dunn Manufacturing Co 10(J BMS39 Structural Properties of a Wall Construction of "Pfeifer Units" Sponsored by the Wisconsin Units Co 10<f BMS40 Structural Properties of a Wall Construction of "Knap Concrete Wall Units"

Sponsored by Knap America, Inc 10^ BMS41 Effect of Heating and Cooling on the Permeability of Masonry Walls * BMS42 Structural Properties of Wood-Frame Wall and Partition Constructions with

"Celotex" Insulating Boards Sponsored by The Celotex Corporation 15(* BMS43 Performance Test of Floor Coverings for Use in Low-Cost Housing: Part 2 15<- BMS44 Surface Treatment of Steel Prior to Painting 10<f BMS45 Air Infiltration Through Windows » 154 BMS46 Structural Properties of "Scott-Bilt" Prefabricated Sheet-Steel Constructions for Walls, Floors, and Roofs Sponsored by The Globe-Wernicke Co lO^i BMS47 Structural Properties of Prefabricated Wood-Frame Constructions for Walls, Partitions, and Floors Sponsored by American Houses, Inc lOi^ BMS48 Structural Properties of "Precision-Built" Frame Wall and Partition Constructions Sponsored by the Homasote Co 15^ BMS49 Metallic Roofing for Low-Cost House Construction 154 BMS50 Stability of Fiber Building Boards as Determined by Accelerated Aging 10<t BMS51 Structural Properties of "Tilecrete Type A" Floor Construction Sponsored by the

Tilecrete Co 10<f BMS52 Effect of Ceiling Insulation Upon Summer Comfort .'. 10«s BMS53 Structural Properties of a Masonry Wall Construction of "Munlock Dry Wall

Brick" Sponsored by the Munlock Engineering Co 10^ BMS54 Effect of Soot on the Rating of an Oil-Fired Heating Boiler 1(H

BMS55 Effects of Wetting and Drying on the Permeability of Masonry Walls 104 BMS56 A Survey of Humidities in Residences lOt BMS57 Roofing in the United States—Results of a Questionnaire * BMS58 Strength of Soft-Soldered Joints in Copper Tubing.... 10^ BM1S59 Properties of Adhesives for Floor Coverings 10^ BMS60 Strength, Absorption, and Resistance to Laboratory Freezing and Thawing of Building Bricks Produced in the United States , 15^ BMS61 Structural Properties of Two Nonreinforeed Monolithic Concrete Wall Constructions .- ,. 10^ BMS62 Structural Properties of a Precast Joist Concrete Floor Construction Sponsored

by the Portland Cement Association 104 BMS68 Moisture Condensation in Building Walls 15^ BMS64 Solar Heating of Various Surfaces * BMS65 Methods of Estimating Loads in Plumbing Systems 15^

BMS66 Plumbing Manual * BMS67 Structural Properties of "Mu-Steel" Prefabricated Sheet-Steel Constructions for Walls, Partitions, Floor, and Roofs Sponsored by Herman A. Mugler 15^ BMS68 Performance Test for Floor Coverings for Use in Low-Cost Housing: Part 3 204

BMS69 Stability of Fiber Sheathing Boards as Determined by Accelerated Aging 10^ BMS70 Asphalt-Prepared Roll Roofings and Shingles 204

fiMS71 Fire Tests of Wood- and Metal-Framed Partitions i 204

BMS72 Structural Properties of "Precision-Built, Jr." Prefabricated Wood-Frame Wall

Construction Sponsored by the Homasote Co 104 BMS73 Indentation Characteristics of Floor Coverings 104 BMS74 Structural and Heat-Transfer Properties of "U. S. S. Panelbilt" Prefabricated

Sheet-Steel Constructions for Walls, Partitions, and Roofs Sponsored by the Tennessee Coal, Iron & Railroad Co 154 i^o"^^ Survey of Roofing Materials in the North Central States 154

Effect of Outdoor Exposure on the Water Permeability of Masonry Walls 15^ BMS77 Properties and Performance of Fiber Tile Boards 10^ BMS78 Structural, Heat-Transfer, and Water-Permeability Properties of Five Earth-Wall

Constructions 254 BMS79 Water-Distributing Systems for Buildings 204

Performance Test of Floor Coverings for Use in Low-Cost Housing: Part 4 15^ BMbSl Field Inspectors' Check List for Building Constructions (cloth cover, 5x7%

mches)

„.

204

[List continued on cover page rv]
BUILDING MATERIALS AND STRUCTURES REPORTS

[Continued from cover page iii] BMS82 Water Permeability of Walls Built of Masonry Units „ 204 BMS83 Strength of Sleeve Joints in Copper Tubing Made With Various Lead-Base Solders 104 BMS84 Survey of Roofing Materials in the South Central States „ * BMS86 Dimensional Changes of Floor Coverings with Changes in Relative Humidity and

Temperature 104 BMS86 Structural, Heat-Transfer, and Water-Permeability Properties of "Speedbrik"

Wall Construction Sponsored by the General Shale Products Corporation 15^ BMS87 A Method for Developing Specifications for Building Construction—Report of Subcommittee on Specifications of the Central Housing Committee on Research, Design, and Construction 15^

BMS88 Recommended Building Code Requirements for New Dwelling Construction With

Special Reference to War Housing , * BMS89 Structural Properties of "Precision-Built, Jr." (Second Construction) Prefabricated Wood-Frame Wall Construction Sponsored by the Homasote Co, : 16^ BMS90 Structural Properties of "PHC" Prefabricated Wood-Frame Constructions for Walls, Floors, and Roofs Sponsored by the PHC Housing Corporation 15^ BMS91 A Glossary of Housing Terms 15^ BMS92 Fire-Resistance Classifications of Building Constructions. „ 304

BMS93 Accumulation of Moisture in Walls of Frame Construction During Winter Exposure 104 BMS94 Water Permeability and Weathering Resistance of Stucco-Faced, Gunite-Faced,

and "Knap Concrete-Unit" Walls 104 BMS95 Tests of Cement-Water Paints and Other Waterproofings for Unit-Masonry Walls 15^ BMS96 Properties of a Porous Concrete of Cement and Uniform-Sized Gravel 10^ BMS97 Experimental Dry-Wall Construction With Fiber Insulating Board 10^5 BMS98 Physical Properties of Terrazzo Aggregates , 15^ BMS99 Structural and Heat-Transfer Properties of "Multiple Box-Girder Plywood Panels"

for Walls, Floors, and Roofs 15^ BMSlOO Relative Slipperiness of Floor and Deck Surfaces 104 BMSlOl Strength and Resistance to Corrosion of Ties for Cavity Walls 104 BMS102 Painting Steel 104

BMS103 Measurements of Heat Losses From Slab Floors...., 10^ BMS104 Structural Properties of Prefabricated Plywood Lightweight Constructions for Walls, Partitions, Floors, and Roofs Sponsored by the Douglas Fir Plyv/ood

Association 254

BMS105 Paint Manual $1.00

BMS106 Laboratory Observations of Condensation in Wall Specimens * BMS107 Minimum Requirements for New Dwelling Construction 204

BMS108 Temperature Distribution in a Test Bungalow With Various Heating Devices 104 BMS109 Strength of Houses: Application of Engineering Principles to StructuraL Design.. ** BMSllO Paints for Exterior Masonry Walls. 104

•Out of print

**No-vr in print.